Transitive authentication authorization accounting in the interworking between access networks

ABSTRACT

A method and a system for allowing a user device that has already been authenticated by a first communications network to gain access to a second communications network without undergoing authentication by the second communications network. The first communications network and the second communications network have a pre-established trust relationship there between. A packet is received from the user device that includes a user device public key, by the second network via the first network. A session key is sent from the second network to the user device, via the first network, when a source Internet Protocol (IP) address associated with the packet falls into a range allocated to the first network. The session key is encrypted with the user device public key. The user device decrypts the session key using a private key and uses the session key thereafter to access the second network. Further a mapping is generated to correlate the identity of the user device with the session key such that usage data relate to user device is generated by the second communications network and transmitted to the first communications network, which generates accounting information indicative of user device access of the second communications network.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to networking and, more particularly, to method for transitive Authentication Authorization and Accounting (AAA) in the interworking between access networks.

2. Background of the Invention

Typically, Authentication, Authorization and Accounting (AAA) are required to access and utilize networks such as cellular networks and Wireless Local Area Networks (WLANs). In an environment in which a mobile terminal has multiple network access mechanisms, providing AAA interworking among these networks is of great importance. However, it is generally the case that one or more of the involved networks have a closed AAA scheme and it is difficult for one of the networks to use the AAA structure of another one of the networks and vice versa. For example, cellular networks have an AAA infrastructure that is not compatible with Internet based AAA and cannot be easily accessed through Internet protocols, even though the involved networks (including the cellular networks) have external IP connectivity.

Convention approaches for providing AAA interworking all require a special interworking function between the networks, even for AAA interworking between networks that have pre-established trust relationships amongst themselves. Using this interworking function, e.g., network B will then access network A's AAA infrastructure to authenticate a user which has already been authenticated by network A (through a closed network AAA mechanism). The conventional approaches do not take advantage of the fact that the user has already been authenticated by network A which has pre-established trust relationship with network B.

Accordingly, it would be desirable and highly advantageous to have a method for transferring the trust that is attributed to a user by one network from that network to another network, particularly without requiring any special interworking function to accomplish the same.

SUMMARY OF THE INVENTION

The problems stated above, as well as other related problems of the prior art, are solved by the present invention, a method for transitive Authentication Authorization and Accounting (AAA) in the interworking between access networks.

According to an aspect of the present invention, there is provided a method for allowing a user device that has already been authenticated by a first network to gain access to a second network. The first network and the second network have a pre-established trust relationship there between. A packet is received from the user device that includes a user device public key, by the second network. A session key is sent from the second network to the user device when a source Internet Protocol (IP) address associated with the packet falls into a range allocated to the first network. The session key is encrypted with the user device public key. The session key is for permitting the user device to access the second network.

These and other aspects, features and advantages of the present invention will become apparent from the following detailed description of preferred embodiments, which is to be read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating a computer system 100 to which the present invention may be applied, according to an illustrative embodiment of the present invention;

FIG. 2 is a block diagram illustrating a transitive AAA structure to which the present invention may be applied, according to an illustrative embodiment of the present invention;

FIG. 3 is a flow diagram illustrating an AAA method for allowing a user device that has been authenticated by a 3G cellular network to gain access to a Wireless Local Area Network WLAN, according to an illustrative embodiment of the present invention; and

FIG. 4 is a flow diagram illustrating an accounting method for performing an accounting for the user of the user device of the method of FIG. 3, according to an illustrative embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to a transitive Authentication Authorization and Accounting (AAA) scheme for an interworking between access networks. It is to be appreciated that the present invention is applicable to any combination of access networks. However, the present invention is particularly applicable to cellular network and Wireless Local Area Network (WLAN) interworking.

The present invention transfers the trust on a user by a first access network to a second access network where the first and the second access networks have a pre-established trust relationship. In contrast to the prior art, the present invention does not require any special interworking function between the two networks, but rather relies on IP addressing and routing schemes to verify user access right. It is to be appreciated that the present invention is also referred to herein as transitive AAA.

It is to be understood that the present invention may be implemented in various forms of hardware, software, firmware, special purpose processors, or a combination thereof. Preferably, the present invention is implemented as a combination of hardware and software. Moreover, the software is preferably implemented as an application program tangibly embodied on a program storage device. The application program may be uploaded to, and executed by, a machine comprising any suitable architecture. Preferably, the machine is implemented on a computer platform having hardware such as one or more central processing units (CPU), a random access memory (RAM), and input/output (I/O) interface(s). The computer platform also includes an operating system and microinstruction code. The various processes and functions described herein may either be part of the microinstruction code or part of the application program (or a combination thereof) which is executed via the operating system. In addition, various other peripheral devices may be connected to the computer platform such as an additional data storage device and a printing device.

It is to be further understood that, because some of the constituent system components and method steps depicted in the accompanying Figures are preferably implemented in software, the actual connections between the system components (or the process steps) may differ depending upon the manner in which the present invention is programmed. Given the teachings herein, one of ordinary skill in the related art will be able to contemplate these and similar implementations or configurations of the present invention.

FIG. 1 is a block diagram illustrating a computer system 100 to which the present invention may be applied, according to an illustrative embodiment of the present invention. The computer processing system 100 includes at least one processor (CPU) 102 operatively coupled to other components via a system bus 104. A read only memory (ROM) 106, a random access memory (RAM) 108, a display adapter 110, an I/O adapter 112, a user interface adapter 114, a sound adapter 199, and a network adapter 198, are operatively coupled to the system bus 104.

A display device 116 is operatively coupled to system bus 104 by display adapter 110. A disk storage device (e.g., a magnetic or optical disk storage device) 118 is operatively coupled to system bus 104 by I/O adapter 112. A mouse 120 and keyboard 122 are operatively coupled to system bus 104 by user interface adapter 114. The mouse 120 and keyboard 122 are used to input and output information to and from system 100.

At least one speaker (herein after “speaker”) 197 is operatively coupled to system bus 104 by sound adapter 199.

A (digital and/or analog) modem 196 is operatively coupled to system bus 104 by network adapter 198.

FIG. 2 is a block diagram illustrating a transitive AAA structure to which the present invention may be applied, according to an illustrative embodiment of the present invention. In the illustrative embodiment of FIG. 2, the transitive AAA structure includes: a first network 210; a second network 220; the Internet 230, and a user device 240. The second network 220 includes an AAA server 220 a. The user device 240 includes a first network interface 240 a and a second network interface 240 b. It is to be appreciated that while the present invention is described herein with respect to two networks, the present invention may be applied with any number and any types of networks, while maintaining the spirit and scope of the present invention.

For the purpose of illustrating the present invention, the following description thereof is made with respect to two networks, a 3G cellular network and a Wireless Local Area Network (WLAN). However, it is to be appreciated that the present invention may be applied to any number of networks in combination as well as any type of network, while maintaining the spirit and scope of the present invention.

In the illustrative example, user device 240 has dual radio interfaces for accessing the 3G network and the WLAN. According to the present invention, user device 240 is able to access WLAN 220 via the AAA mechanism of the 3G network 210 as follows. Upon detection of WLAN 220, user device 240 determines whether WLAN 220 supports transitive AAA. If so, user device 240 sends a registration message to the 3G network via path 212. The registration message includes a user public key. The registration message is transmitted to WLAN server 230 a via the Internet as indicated by paths 216 and 222. Upon receiving the registration message, WLAN server 230 a checks the source IP address to determine whether the received address is within a range of address for which transitive AAA is supported. If so, WLAN server 230 provides a session key that is encrypted with the user device public key and transmits the session key to 3G network 210 via the Internet as indicated by paths 224 and 218. The 3G network than transmits the session key to user device 240 as indicated by path 214. User device 240 then decrypts the session key using a user device private key and is able to gain access to WLAN 220 using the session key.

In this manner, user device 240 is able to gain access to WLAN 220 via the AAA mechanism of 3G network 210, as long as WLAN 220 supports transitive AAA and has a pre-existing trust relationship with 3G network 210. The present invention provides a mechanism for allowing a user device 240 to “roam” between WLANs that have a pre-existing relationship with the 3G network by directly using the AAA mechanism of the 3G network rather than having the WLAN contact the 3G AAA services for authentication or using the AAA mechanism associated with each WLAN.

The 3G cellular network is allocated a range of IP addresses; when the user uses the 3G cellular network for IP access, the source IP address will fall into this range. Given the routing scheme of the Internet, while any snooper can fake such a source IP address, when a return IP packet is sent, it can only be received by the user that actually has the IP address, unless the snooper can break into the routers that forward the IP packets. Thus, the present invention may provide an additional measure of security.

FIG. 3 is a flow diagram illustrating an AAA method for allowing a user device that has been authenticated by a 3G cellular network to gain access to a Wireless Local Area Network WLAN, according to an illustrative embodiment of the present invention. The user device has two radio access interfaces (3G cellular and WLAN). The 3G cellular network and the WLAN have a pre-established trust relationship there between.

Upon the user device moving into an area under the coverage of the WLAN, it is determined (e.g., by the WLAN interface of the user device) whether the WLAN supports transitive MA and whether the 3G cellular network has a pre-established trust relationship with the WLAN (e.g. through broadcasting or Dynamic Host Configuration Protocol (DHCP)) (step 302). If not, then the method is terminated. Otherwise, step 304 is performed as described herein below and then the method proceeds to step 305. At step 305, the IP address of an AAA server of the WLAN (hereinafter WLAN MA server) is obtained by the user device (step 305).

A User Datagram Protocol (UDP) packet that includes a registration message is sent from the user device to the WLAN MA server, e.g., through the 3G cellular interface of the user device (step 310). It is to be appreciated that while step 310 is described with respect to a UDP packet, any type of packet may be employed including, but not limited to, a Transmission Control Protocol (TCP) packet. The registration message includes the WLAN address (e.g. Medium Access Control (MAC) address or IP address of the WLAN interface) of the user device, and the public key of the user device.

Upon receiving the registration message, the WLAN AAA server determines whether the source IP address of the registration message (e.g., an IP address of the 3G interface) falls into a range allocated to the 3G cellular network with which the WLAN network has a pre-established relationship (step 315). If not, then the method is terminated. Otherwise, the WLAN AAA server sends back a confirmation message to the 3G cellular interface of the user device (step 320). The confirmation message includes a session key that is to be used between the user device and the WLAN (session key permits the user device to access the WLAN); the session key is encrypted with the public key of the user device. The WLAN AAA server also registers a mapping between the WLAN address of the user device and the (assigned) session key (step 325). Step 325 is performed so that a given session key is associated with a corresponding user.

Upon receiving the confirmation message (e.g., via the 3G cellular interface of the user device), the session key is decrypted using a private key of the user device (step 328). Using the session key, access to the WLAN is obtained by the user device (step 330).

A description will now be given of a possible collaborative hacker attack on the method of FIG. 3. It is to be appreciated that the following attack is possible due to the use of IP addressing and IP routing without additional authentication support from the 3G cellular network. A hacker sends a registration message with a fake IP address that falls into the range of the 3G cellular network. The hacker then intercepts the confirmation message somewhere along the route between the WLAN and the 3G cellular core network. The hacker notifies another hacker within the WLAN coverage about the discovered key.

However, it is very difficult to accomplish the above attack, especially the step of intercepting the confirmation message. The hacker has to gain access to a router along the route between the WLAN and the 3G network, just for the purpose of obtaining a session key, and the two hackers have to collaborate to carry out the attack (assuming that a hacker within the coverage of the WLAN cannot get access to any of the routers discussed above because if the hacker could obtain access, then there would have been no point of carrying out the attack since the hacker would already have had Internet access).

To prevent the preceding collaborative hacker attack, step 304 is performed in the method of FIG. 3. At step 304, a secure IP channel (e.g. an Internet Protocol (IP) Security (IPSec) tunnel) is established between the WLAN AAA server and a Gateway General Packet Radio Service (GPRS) Serving/Support Node (GGSN) of the 3G cellular network. Since the path is also secure between the user and the GGSN of the 3G cellular network (as ensured by the 3G network security), the above attack can be thwarted.

A description will now be given of an accounting method that may be employed along with the method of FIG. 3, according to an illustrative embodiment of the present invention. FIG. 4 is a flow diagram illustrating an accounting method for performing an accounting for the user of the user device of the method of FIG. 3, according to an illustrative embodiment of the present invention.

It is determined whether the IP address of the 3G cellular interface of the user device is a static IP address (step 405). If so, the identity of the user is determined based upon the IP address of the 3G cellular interface, (step 410), and the method proceeds to step 450. Otherwise (the IP address is dynamic), the identity of the user is determined from a mapping between the (temporary) IP address of the 3G cellular interface and the actual ID of the user (step 415), and the method proceeds to step 450. At step 450, an accounting step is performed with respect to the user based on the IP address of the 3G cellular interface (static IP address) or the mapping (dynamic IP address).

It is to be appreciated that for the purposes of the present invention, Network Address Translation (NAT) is treated the same as if the IP address of the 3G cellular interface were dynamic. Moreover, with respect to the mapping referred to at step 415 above, such mapping may be stored, e.g., at a DHCP server or a NAT server if NAT is used. It is to be further appreciated that the present invention is not limited to the use of mappings to determine user identity in the case of non-static IP address and, thus, other approaches may be employed, while maintaining the spirit and scope of the present invention.

Although the illustrative embodiments have been described herein with reference to the accompanying drawings, it is to be understood that the present invention is not limited to those precise embodiments, and that various other changes and modifications may be affected therein by one skilled in the art without departing from the scope or spirit of the invention. All such changes and modifications are intended to be included within the scope of the invention as defined by the appended claims. 

1. A method for allowing a user device to gain access to a wireless LAN, comprising the steps of: receiving from a user device, via a second communications network, a registration message that includes a user device public key, the user device having been authenticated by the second communications network, the wireless LAN having a pre-established trust relationship with the second communications network, wherein said second communications network is a cellular network; and determining whether a source IP address received from the second communication network is within a predetermined range of IP source addresses, and if so, generating a session key in response to the user device public key, the session key adapted to be decrypted using a user device private key, transmitting the session key to the second communications network, and allowing the user device to gain access to the wireless LAN using the session key.
 2. The method according to claim 1, further comprising the step of establishing a secure IP channel between the wireless LAN and the cellular network.
 3. The method according to claim 1, further comprising the steps of receiving an address of an interface associated with the user device, and registering a mapping between the address and the session key.
 4. The method according to claim 3, wherein the address comprises one of a Medium Access Control (MAC) address and an Internet Protocol (IP) address.
 5. The method according to claim 3, further comprising the steps of generating usage data in response to the accessing of the communications network by the user device, and transmitting the usage data to the second communications network, whereby accounting information for the user device can be generated in response to the usage data.
 6. A wireless LAN, comprising: first means for communicating with a user device; second means for communicating with a communications network, wherein said communications network is a cellular network; means, coupled to the second means for communicating, for receiving a registration message that includes a user device public key, for determining whether a source IP address associated with the registration message is within a range of predetermined source IP addresses; and means, coupled to the determining means and the second means for communicating, for generating a session key encrypted using the user device public key if the source IP address is within the range, and transmitting the session key to the user device via the second means for communicating, wherein the first communicating means allows user device access to the wireless LAN using the session key.
 7. The wireless LAN according to claim 6, further comprising memory means for mapping an interface address associated with the user device with the session key, and means for generating usage data in response to user device access of the wireless LAN and for transmitting the usage data to the communications network.
 8. A method for accessing a wireless LAN using a user de vice, comprising the steps of: establishing communications with a first communications network and performing an authentication step with the first communications network, wherein said first communications network is a cellular network; transmitting a registration message that includes a user device public key to the first communications network; receiving from the first communications network a session key received from the wireless LAN; and decrypting the session key with a private key; and establishing access to the wireless LAN using the session key.
 9. The method according to claim 8, wherein the registration message includes an address associated with an interface for communicating with the wireless LAN, whereby a mapping can be generated for the address and the session key.
 10. The method according to claim 9, wherein the address comprises one of a Medium Access Control (MAC) address and an Internet Protocol (IP) address.
 11. The method according to claim 8, further comprising the step of receiving accounting information regarding the user device access to the wireless LAN via either the wireless LAN or the cellular network.
 12. The method according to claim 8, further comprising the step of initially determining whether the first communications network has a pre-established trust relationship with the wireless LAN.
 13. A method for allowing a user device in communication with a first communications network to gain access to a second communications network, the first communications network and the second communications network having a pre-established trust relationship there between, the method comprising the steps of: authenticating the user device within the first communications network, wherein the first communications network comprises a cellular network and the second communications network comprises a wireless LAN network; receiving (310) from the user device a registration message that includes a user device public key; transmitting (310) a message that includes the user device public key and a source address that falls within a predetermined range allocated to the first communications network to the second communications network; receiving (320) a session key from the second communications network; and transmitting (320) the session key to the user device, wherein the session key allows the user device to gain access to the second communications network.
 14. The method according to claim 13, further comprising the step of establishing a secure IP channel between the first communications network and the second communications network to prevent unauthorized interception of the session key.
 15. The method according to claim 13, further comprising the step of receiving an address of an interface associated with the user device, and registering a mapping between the interface and the session key.
 16. The method according to claim 15, wherein the address of the interface comprises one of a Medium Access Control (MAC) address and an Internet Protocol (IP) address.
 17. The method according to claim 13, further comprising the step of receiving usage data from the second communications network indicative of user device access of the second communications network and generating accounting information associated with the user device based on the usage data.
 18. The method according to claim 13, wherein the session key is encrypted using the user device public key, and is adapted to be decrypted using a user device private key. 